In one aspect, the present invention addresses the need for improved target utilization. Uptime and efficient use of material are important economical aspects of sputtering technology; the invention allows to enhance this aspect.
In another aspect the present invention is based on the need for depositing a film having a homogeneous thickness distribution, by means of sputter coating. In this respect the invention is useful for target arrangements of different sizes; be it single targets or large-area targets mounted from several longitudinally extended single targets side by side.
In a sputtering process, ions obtained from a working gas, typically Argon, are accelerated in an electric field towards a sputtering target comprising a sputtering material, and impinge on a sputtering surface of the target, and thereby remove material from the target.
In magnetron sputtering, be it reactive or non-reactive, a target arrangement may comprise a mounting plate and a target plate bonded to it, especially in the case of brittle, sintered material. The upside of the target plate defines the sputtering surface. The target is sputter-eroded along so-called “race tracks”. On the sputtering surface a closed-loop, erosion furrow or trench is created due to closed-loop, tunnel-shaped magnetic fields (“magnetron magnetic fields”) existing above the target and produced by magnet arrangements behind the target. These magnetic fields confine zones with elevated plasma density, which again act as electron traps. Such magnetic fields known in the art tend to generate very deep erosion at the edges and this is limiting the overall target utilization. The target lifetime is short, since the area of maximum erosion will limit the usability of the whole target. In order to improve the utilization of the target, the magnetron magnetic field can be moved relative to the sputtering surface.
U.S. Pat. No. 6,416,639 discloses a magnetron sputtering arrangement with such a relative movement. For further improvement of the deposition uniformity, U.S. Pat. No. 6,416,639 discloses the use of ferromagnetic pieces, which are fixed relative to the target, so as to alter the magnetic field, to which the sputtering surface is exposed (superposition of magnetron magnetic field and the field of the ferromagnetic pieces). Furthermore, U.S. Pat. No. 6,416,639 discloses various shapes of paths along which the relative movement can take place.
In DE 27 07 144 A1, further shapes of paths along which the relative movement can take place are disclosed.
Prior Art in general often addresses the issue of target utilization and film homogeneity with different focus, because sometimes proposed solutions can only fulfill one criterion. However, under today's needs both aspects are crucial, with regard to quality of the product (film homogeneity) and economical aspects (yield, maintenance, uptime, target utilization).